Plastic impregnated fabric journal bearing

ABSTRACT

The invention contemplates an improved method of making fabriclined journal bearings, of bore size determined by a mandrel. A piece of low-friction fabric material is cut from rectilinear stock, to such length between cut-off ends as to substantially equal the peripheral extent of the mandrel. A piece of bondable fabric is secured, as by sewing or clamping, to a cut-off end of the low-friction piece. The fabric composite, impregnated with hardenable material, is then wrapped onto the mandrel, beginning with the low-friction piece. The assembly is thereafter cured to hardness, and the mandrel removed.

United States Patent [191 Conru 11 3,734,55 51 May 22, 1973 [54] PLASTICIMPREGNATED FABRIC JOURNAL BEARING [75] Inventor: Harold Ward Conru,South Burlington, Vt.

[73] Assignee: Textron Inc., Providence, RI.

[22] Filed: Sept. 25, 1971 [21] Appl. No.: 18,389

Related U.S. Application Data [62] Division of Ser. No. 703,702, Feb. 7,1968.

[52] U.S. Cl. ..308/238, 156/93, 156/192 [51] Int. Cl. ..Fl6c 33/20 [58]Field of Search ..308/238; 156/93, 156/192; 130/151,152,156,162,163,166, 168

[56] References Cited UNITED STATES PATENTS 3,507,023 4/1970 Matt et al...308/238 X 3,053,592 9/1962 Runton et al ..308/238 3,110,530 11/1963Herman "308/238 3,231,460 1/1966 Andrews .....308/238 3,250,556 5/1966Couch et a1. ..308/238 3,328,101 6/1967 Sullivan, Jr ..308/238 3,635,256l/1972 McLarty ..308/238 Primary Examiner-Charles J. Myhre AssistantExaminerBarry Grossman Att0rneyllopgood & Calimafde [57] ABSTRACT Theinvention contemplates an improved method of making fabric-lined journalbearings, of bore size determined by a mandrel. A piece of low-frictionfabric material is cut from rectilinear stock, to such length betweencut-off ends as to substantially equal the peripheral extent of themandrel. A piece of bondable fabric is secured, as by sewing orclamping, to a cut-off end of the low-friction piece. The fabriccomposite, impregnated with hardenable material, is then wrapped ontothe mandrel, beginning with the low-friction piece. The assembly isthereafter cured to hardness, and the mandrel removed.

5 Claims, 7 Drawing Figures PATENTEB WIYZZ 3 7 34, 585

Mia/0 W g w ATTO N EYS PLASTIC IMPREGNATED FABRIC JOURNAL BEARING Thisapplication is a division of my copending application, Ser. No. 703,702,filed Feb. 7, 1968.

This invention relates to a method of making a journal bearing in whichlow-friction fabric material is relied upon to achieve low-friction atthe bore of the hearing.

In the field of plastic bearings wherein reliance is placed onlow-friction properties in certain synthetic fibers to achieve lowfriction in bearing operation, it is known to rely on composite ordouble-woven fabric in which two different materials are woven together,namely, a low-friction material such as fibrous polytetrafluoroethylene(Teflon), and a bondable material such as cotton; linen, fiberglass, orthe like. The fabric is impregnated with phenolic, epoxy or otherhardenable material and is then cured to hardness in the desired shape.The fabric is woven so as to expose the low-friction fibers at thebearing face, when molded or otherwise shaped.

In using such materials for journal bearings, a strip of the fabric isimpregnated with the hardenable material and then wrapped on a mandrelto desired build-up thickness, as a spiral development about themandrel. Although this technique is effective in terms of technicalproficiency of the ultimate product, it is unnecessarily wasteful of thelow-friction fiber. Proposals haye been made to save the low-frictionfiber by specially weaving a cloth so as to incorporate the low-frictionmaterial near one edge, to a width adequate for peripheral coverage of agiven sized mandrel; but this technique requires costly weaving set-ups,wherein different-width edges must be woven for each journalbearing boresize to be accommodated It is, accordingly, an object of the inventionto pro- 'vide an improved method of making a journal bearing of thecharacter indicated, wherein the utmost economy of low-friction materialcan be realized, without sacrifice tooperational proficiency.

Another object is to achieve the foregoing object with a methodinherently flexibly lending itself to use of the same woven fabrics formanufacture of journal bearings of a wide variety of bore and of outsidediameter sizes.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred embodiments of the invention:

FIG. 1 is a simplified view in perspective showing a journal bearing ofthe invention, the exposed end face being shown cut and in section tobetter illustrate relationships;

FIG. 2 is a perspective to illustrate steps of a first embodiment of themethod of the invention;

FIGS. 3 and 4 are enlarged views in side elevation to illustratealternatives;

FIG. 5 is a view similar to FIGS. 3 and 4, on a reduced scale, toillustrate a further alternative, the parts being shown looselydeveloped in order to avoid ambiguity of identification;

FIG. 6 is a simplified view in longitudinal elevation, partlybroken-away and in section, to illustrate cut-off to desired length; and

FIG. 7 is a flat layout of patterns usable in an alternative employmentof the method of FIG. 2.

Briefly stated, the invention contemplates an improved method of makingfabric-lined journal bearings, of bore size determined by a mandrel. Apiece of lowfriction fabric material is cut from rectilinear stock, tosuch length between cut-off ends as to substantially equal theperipheral extent of the mandrel. A piece of bondable fabric is secured,as by sewing or clamping, to a cut-off end of the low-friction piece.The fabric composite, impregnated with hardenable material, is thenwrapped onto the mandrel, beginning with the low-friction piece. Theassembly is thereafter cured to hardness, and the mandrel removed.

FIG. 1 illustrates the kind of bearing produced by the methods of theinvention. The bearing is a sleeve 10 having a bore 11 with inherentself-lubricating or lowfriction properties determined by such propertiesin a fibrous element of an inner layer 12 of fabric. Outside of thislayer 12 is a convolute development region 13 containing as manywrapped-up turns as desired of a different fabric which, for purposes ofthe invention, will merely be termed a fabric of bondable material, asfor example, cotton-duck, linen, fiberglass, and the like. The solidityof the bearing is determined by an impregnation with hardenable materialsuch as phenolic, epoxy or the like, and the sectioning for plastic forboth regions 12-13 will be understood to apply for the employment ofessentially a single body of hardening plastic permeating all layers ofweave and cured to ultimate hardness.

In FIG. 2, I illustrate that the bearing 1 may be made in reference to acylindrical mandrel 15 having a periphery precisely finished todetermine the ultimate bore in the desired bearing. The low-frictionmaterial used in the inner layer 12 is in FIG. 2 a single rectangularpiece 16 of suitable low-friction fabric. This piece 16 is intended forcircumferential envelopment of the mandrel 15 and in accordance with theinvention need be no longer than substantially this circumferentialextent. The piece 16 may thus be cut from a bolt or other rectilinearpiece of the fabric so as to define a length between cut-off edges 17and 18 which represents substantially the periphery of the mandrel 15.The fabric 16 may be one of a variety of known materials. For example,it may be all of low-friction material, such as for example, a weave ofall-Teflon, etched or otherwise treated, as desired for greaterbondability. On the other hand, it may be a composite of Teflon andbondable or filler material wherein the filler materials are twistedwith the Teflon to make the threads from which the fabric is woven, orwherein the fabric is double-woven to expose substantially only theTeflon threads at the inner face (i.e., at the bore 11) and the bondablethreads at the outer face (i.e., adjacent the outer wrapup layers 13).

The bondable material 19 in FIG. 2 may be as previously indicated and ofwidth W corresponding with the width of the piece 16. In FIG. 2, thecorresponding edges of the low-friction material 16 and the bondablematerial 19 are secured by sewing together, as indicated by thestitching at 18.

To fabricate the illustrated bearing by the step in FIG. 2, thecomposite cloth, i.e., the cloth of stitched pieces 16-19, is firstsoaked in liquid plastic material (which need only be calledhardenable); and it is then laid upon the mandrel 15 to enablecircumferential envelopment, as suggested by the almost completed turnof such development in FIG. 2. The mandrel is then caused to rotate inthe direction shown by the arrow, causing the seam at 18 tosubstantially match the outer edge 17; thereafter, the bondable materialmerely wraps in successive layers around the low-friction lining. Thisprocess is continued until the desired radial thickness of build-up isachieved, and preferably the lay-up is under tension so as to achieve atight compaction of the fabric layers.

Upon completion of the desired radial build-up, the

wrapped mandrel may be placed in a cylindrical mold (not shown) and thehardenable material subjected to a curing process, to the point of fullyhardening the as sembly. The wrapped mandrel may also be cured, withouta mold, in an oven; such curing may be performed either with or withouthaving first encased the wrapped mandrel in a vacuum bag. Use of thevacuum-bag technique achieves added pressure during the cure, and italso helps remove solvents such as would be required with polyimides.Heat-shrinkable plastic such as mylar or nylon may also be employed tocompress the wrapped mandrel during cure and post cure. After curing,the mandrel is released, release being facilitated by employment of asuitable parting agent as a coating prior to wrap up.

In certain cases, it may be desired, alternatively, to impregnate thepieces 16 and 19 independently, and prior to stitching. Thus, theimpregnant and the degree of impregnation may be optimized for therespective pieces 16-19. They can be stitched when their impregnantshave dried and the fabrics are limp (B-stage cured). Final curing toC-stage may be accomplished, as described, after wrap-up on the mandrel.

FIG. 3 illustrates a modification wherein the ends 1718' of thelow-friction piece 16 are first secured by sewing together so as todefine a sleeve for full envelopment of and fit to the mandrel 15. Inthe process of sewing at 20 to achieve the sleeve construction, Iindicate that the adjacent cut-off edge of the bondable material 19' bestitched at the same time.

The embodiment of FIG. 4 illustrates that the method of FIG. 3 lendsitself to the ready employment of a layer of barrier material 21interposed between the sleeve of low-friction material 16" and the firstlayer of wrap-up of the bondable material 19". Of course, the barriermaterial 21 may be pre-cut substantially to occupy the availablecircumferential extent between the respective sewn ends of the sleeve16" (designated generally 22) and, once the rotation is started forwrap-up of the bondable fabric over the low-friction fabric, the barrierlayer is neatly sandwiched between. As before, convolute developmentcontinues untill the full radial thickness is achieved.

The material of barrier layer 21 may be a woven fabric, an uncuredplastic-soaked paper sheet, or heatfusible material which cures fasteror at a lower temperature than the fabric impregnant. The point of thebarrier layer 21 is to impede flow of impregnant from the outer layers13 to the inner layer 12 during the curing process, thereby assuringthat the desired quantity of impregnant will remain in the inner layer12, and bleed through" to the bearing surface can be controlled oravoided, as desired.

FIG. 5 illustrates a method similar to those of FIGS. 3 and 4, in thatboth ends l7"'l8"' of the lowfriction piece 16 are the only sewn parts,defining a sleeve to fit the mandrel l5. Seam allowance at ends 17 "'l8"is adequate to permit folding of each end l7-18"' back on itself, awayfrom stitching 20. However, I have found that the bondable material 19"may be adequately secured to the low-friction sleeve if the inner edge23 is first folded or crimped or creased and then pinched under theadjacent low-friction flap or seam allowance 18". This pinched relationshould be held as bondable strip 19 is wrapped around sleeve 16" andinto tightly drawn clamped relation over the seam of sleeve 16.Thereafter, tight application of successive turns merely enhance thetightly secured, clamped engagement of bondable material 19" to thelowfriction sleeve 16", all the way from the initially clamped lead edge23.

FIG. 6 illustrates a method of cut-off to desired length to providejournal bearings as needed from the basic elongated composite curedassembly, fabricated by one of the methods of FIGS. 2 to 5. Thiscomposite assembly is suggested at 25 as being chucked at 26 on a lathe.A first cut-off tool such as the boring tool 27 is positioned by its barsupport 28 at the desired axial penetration within the bore of theassembly 25. At this location, the first phase of cut-off is achieved byradially outward displacement of the cut-off tool 27 to a radial extentd at least as great as, and preferably slightly exceeding, the radialdepth occupied by the lowfriction layer 12. The cut-off tool 27 is shownas a broad V-shape and will be appreciated as serving the purpose ofdefining ultimate bevel surfaces in the finished bearing. Such a bevelsurface is shown at 29, and will be understood to have been formedduring the previous cut-off operation on the piece of assembled stock25. At 30, I schematically suggest the tool mounting to achieve thisfirst stage of cut-off.

The second stage of cut-off is suggested by a tool 31 (and associateddirectional arrow) at the same axial location as that shown for theinternal V-counterboring cut generated by tool 27; it is preferred thatthe thickness, width, or axial extent of the cut-off at 31 shall besubstantially less than that of the V which is generated by tool 27.Such a relationship assures a substantial bevel 29 at each axial end ofthe cut-off pieces; such bevels, to the depth d indicated, avoid orreduce the possibility of low-friction fibers such as Teflon fibersbeing exposed at the axial end planes of the cut-off bearing elements.As an alternative, a rotated fiberglass cut-off wheel may be employed;in such case, the tool 31 identifies such wheel, and the boring tool 27may be optional.

In FIG. 7, I illustrate a modification of the method of FIG. 2 whereinthe pieces to be wrapped-up are cut on a bias. Thus, the low-frictionpiece 35 is of parrallelogram shape for wrapping immediately adjacentthe mandrel 15. The bias of the cut-off edges is shown to the extent D,corresponding to the circumferential extent of the mandrel 15. The slopeof this bias will depend upon the ultimate length W of the assembly. Ofcourse, the bias cut on the bondable material 36 should match that ofthe low-friction material to permitthere be substantial manufacturingeconomy through use of the low-friction material only at the bearingsurface, but a given supply of such low-friction material may be cut asneeded to serve bearing production for a variety of bore sizes andouter-diameter sizes. The same cured tubular basic stock serves ultimatebearings of a variety of lengths, as called for by the customer.Furthermore, the use of separate low-friction stock 16 and bondablestock 19 permits optimized impregnation of each stock (16l9) and curingto dry limp form, prior to cut-off and stitching, without requiring asewn composite strip 16-19 to be subjected to one and the sameimpregnant or degree of impregnation.

Although the invention has been described in connection with thepreferred forms and methods, it will be understood that modificationsmay be made without departing from the scope of the invention as definedin the claims which follow.

What is claimed is:

1. A fabric-lined journal bearing, comprising an inner cylindricalsurface defined by a single layer of fabric of low-friction material,the ends of said single layer being longitudinally stitched to defineoutwardly extending flaps at a generally axially extending seam, and asuccession of circumferential wrappings of a single sheet of bondablefabric wrapped around and bonded to said layer and to each other, theinner end of said single sheet of bondable fabric being secured to saidlayer adjacent one of said flaps.

2. The bearing according to claim 1, in which the inner end of saidbondable sheet is stitched to said single layer adjacent one of saidflaps.

3. The bearing according to claim 1, in which one of said flaps isfolded back alongside adjacent single layer material, and in which theinner end of said bondable sheet is secured between said one flap andsaid adjacent single layer material.

4. The bearing according to claim 3, in which said inner end of saidsheet is secured by the clamping action on said one flap due to saidsuccession of circumferential wrappings.

5. The bearing of claim 1, in which a layer of barrier material isinterposed between said single layer and the adjacent layer of bondablefabric.

2. The bearing according to claim 1, in which the inner end of saidbondable sheet is stitched to said single layer adjacent one of saidflaps.
 3. The bearing according to claim 1, in which one of said flapsis folded back alongside adjacent single layer material, and in whichthe inner end of said bondable sheet is secured between said one flapand said adjacent single layer material.
 4. The bearing according toclaim 3, in which said inner end of said sheet is secured by theclamping action on said one flap due to said succession ofcircumferential wrappings.
 5. The bearing of claim 1, in which a layerof barrier material is interposed between said single layer and theadjacent layer of bondable fabric.